Split view, personal modes, budget warnings, server move script

- Up to three chats side by side (#/s/a+b+c), "Open beside" in the sidebar menu
- File manager tabs of a chat stored per user on the server (/sessions/{id}/tabs)
- Personal modes for every user (Settings → My modes, /account/modes)
- Budget meters (total, provider, images, opencode Go windows) with push warnings
  for admins at the warning share and 100 %, shown in the status overlay
- scripts/move-server.sh: move to another Docker host with bind mounts (Unraid);
  scripts/smoke-test.sh

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/types.ts

@@ -155,7 +155,7 @@ export interface AgentInfo {
   style?: "coding" | "chat";
   model?: string | null;
   tools?: string[] | null;
-  source: "builtin" | "config" | "file";
+  source: "builtin" | "config" | "file" | "personal";
   max_parallel?: number | null;
   refine?: { rounds: number; model?: string | null; criteria?: string | null } | null;
   /** Source file of Markdown agents. */